利用上海浦东站2008年的积分浊度计观测资料,研究超大城市工作和生活环境中气溶胶散射系数的特征及其影响因子.结果表明,人为活动对本站气溶胶的散射系数具有一定影响,工作日的散射系数明显大于休息日.在边界层演变和人为排放的共同作用下,散射系数呈现“双峰一谷”的日变化特征.“周末效应”的计算结果表明,交通排放是形成早晨8-9点散射系数强峰的主要原因,而夜间20-21点的次峰则主要是混合层降低向近地面逆温转化的结果.由于周边环境不同,地面风对本站气溶胶的扩散和输送作用差异明显,导致散射系数在不同风向区间的分布差异非常显著.东风时散射系数随风速增大连续减小,其作用主要表现为扩散降低气溶胶浓度;而西风时,在某些风速区间,散射系数随风速增强而明显增大,人为活动产生的输送对本站气溶胶散射系数具有明显影响.
Aerosol scattering coefficients (ASC) were investigated based upon the nephelometer measurement data at Shanghai Pudong station during 2008. The major factors which have an important influence on the ASC were also studied. The results show that anthropogenic aerosol emissions had significant influence on the variability of the ASC. During weekends (when there are less anthropogenic aerosol emissions), the ASC was much lower than on weekdays. A strong diurnal variation of ASC was observed, with two maxima and one minimum. The first maximum occurred at 8:00-9:00 hours and the second at 20:00-21:00 hours. The minimum occurred at 15:00~16:00 hours. This strong diurnal variation resulted from a combination of the effects of the evolution of the planetary boundary layer (PBL) and anthropogenic aerosol emissions. Traffic emission was a major factor affecting the first maximum in the morning, while the rapid reduction of PBL was a major factor for the formation of the second maximum in the evening. Surface winds (wind speeds and wind directions) played important roles in determining the ASC. During periods with easterly winds, the ASC rapidly decreased with the increase of wind speed, which indicated that aerosols were diluted under strong wind speeds. However, during periods of westerly winds, the ASC was sometimes sustained or even increased with the increase in wind speed, indicating that the aerosol pollution in western Shanghai had an important influence on the ASC in Shanghai.